Protective products and equipment are extremely important and vital for the safety and protection of people to prevent harm or serious injuries resulting from an impact or collision.
In recent decades, the development of protective materials has experienced a major technological advance wherein diverse types of materials are currently used, such as: foams, fibres, and polymeric composites. Despite the great effort in development, the materials used do not efficiently prevent the collateral harm/injuries resulting from impacts. This situation occurs because the materials used do not possess sufficient capacity to absorb the impact energy arising from a collision, this energy being absorbed by the body of the users, causing serious injuries or even death. Furthermore, these types of materials used are generically heavy, rigid, somewhat inflexible and somewhat non-ergonomic.
The use of this kind of materials has different approaches to the absorption of impact energy in the protective products. In the case of fibres and polymeric composites, these have the objective of non-penetration/perforation, not preventing deflection and, in some cases, total rupture of the fibres and polymeric composites occurs. In the case of foams, the objective thereof is absorption of the energy of impact caused by the crash, but they do not prevent perforation; the use of materials having dilating properties (non-Newtonian fluid) is with a view to the reaction of the materials when the latter are subjected to impacts, significantly improving the capacity of absorption of impact energy of the protective products.
Recently, there has been strong interest in research and development in the use of dilating fluids as a material to be incorporated into a personal protective product. Non-Newtonian fluids are often denominated dilating materials. Dilating fluids are materials the properties whereof depend solely on the intensity of the stress applied, that is to say, these materials demonstrate an increase in viscosity with the increase in the stress applied. Dilatancy is a rheological property common to several polymeric systems, although it does not occur in pure polymers and, unlike pseudoplasticity, it depends on the polymeric system considered: solution, suspension, dispersion or emulsion, and is not restricted to a specific particle size.
The development of dilating fluids and the combination thereof with various types of materials has also been studied. The combination between Kevlar fibres and colloidal mixtures using polyethylene glycol (PEG) and nanoparticles of silica, talc and poly(methyl methacrylate) (PMMA) permits increasing the protection against impact. Colloidal solutions, such as clay, quartz, iron oxide, calcareous schist, titanium dioxide, alumina, hematite and barium sulphate have already been studied. It is also possible to obtain non-Newtonian fluids with blood cells, starch and wheat and corn starch. Polymers are also used to produce colloidal solutions; in this case nanoparticles of polyvinylchloride (PVC), poly(styrene-co-acrylonitrile) (PS-AN), polystyrene (PS), poly(methyl methacrylate) (PMMA), poly(styrene-ethyl-acrylate) (PS-EA) and nanofibres of carbon, poly(t-butylstyrene) in mineral oil (3 g/dl), suspension data of styrene-methyl acrylate copolymer (15% by volume) in aqueous solutions of poly(acrylic acid) (1% by weight). Other colloidal solutions studied in the literature were the mixture of nanospheres of poly(styrene-acrylic acid) and ethylene glycol. In the same study, the mixture of nanospheres of poly(styrene-acrylic acid-divinylbenzene) and the same liquid was evaluated. Other dilating materials are polymeric silicones, such as the siloxanes, borate, or polyborodimethylsiloxane (PBDMS) in polyurethane or synthetic elastomers.
The document EP1897609 A2 relates to a composite comprising a non-Newtonian fluid, wherein it is combined with an immiscible or partially-miscible material and wherein the non-Newtonian fluid comprises a suspending fluid and suspended particles having a dimension of less than 10 μm.
The document WO2004103231 A1 describes a product capable of dissipating kinetic energy of a moving object, such as a projectile, and comprises a material having fibres, wherein these are impregnated with particles (polymers, oxides, minerals) suspended in a solvent. These fibres may be of aramid, carbon, nylon, high molecular weight polyethylene, or glass.
The document WO2008115636 A2 describes the production of hollow plastic fibres wherein is incorporated a dilating fluid, the fluids used being based on colloidal systems, more specifically a mixture between polyethylene glycol (PEG) and silica powder.
The document US20050037189 A1 consists of describing a dilating fluid capable of being encapsulated in an elastomeric matrix, more specifically in a foam having closed cells, wherein the dilating fluid is a mixture of a polyurethane foam with polyborodimethilsiloxane (PBDMS) incorporated into an elastomeric polyurethane foam. The company BAE Systems is attempting to develop a solution combining Kevlar fibres with dilating fluids (this fluid being composed of ethylene glycol and silica).
However, in the cases cited there are situations wherein the dilating fluid must be contained or enveloped in a kind of fabric or material and, due to the nature thereof, is not self-sustainable, the resulting products having little flexibility and, in other cases cited, the manufacturing processes are relatively complex and expensive.
These documents illustrate the technical problem to be solved by the present disclosure.